On Saturday 09 February 2008 16:46, kanenas@hawaii.rr.com wrote:
On Saturday 09 February 2008 09:39:13 am Randall R Schulz wrote:
But to go back to the original question (mine), the issue is whether highly over-rated supply is wasteful of power. It appears they are. Randall Schulz I disagree: I looked at a bunch of efficiency plots from 80plus.org. Can you help me find such plots? I really wonder why you first cut out my links and comments while trying to show you were right,
Randall R Schulz wrote: then ask for them again ? You were much more magnanimous in other contributions, which i tagged because i especially liked them :-)
On Saturday 09 February 2008 11:22, Philippe Landau wrote:
Randall R Schulz wrote: It very much depends on the power supply in question. Today i would recommend buying one with over 80% efficiency. These often reach up to 85% efficiency, but only when they operate around 50% load: Power Supplies 101: A comprehensive guide Motherboards.org: http://www.motherboards.org/articles/guides/1487_7.html
The study you quote may be a bit outdated (2002) or be valid for cheap PSUs (Compaq). It is certainly good to check the characteristics of the PSU before you buy one: http://www.80plus.org/manu/psu/manu_psu.htm
But as seen earlier in this thread, calculating the power consumption needs of the components used is not always easy.
Kind regards Philippe
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Switching power-supplies have an efficiency peak when producing about 50% of their maximum rated output. However the curve on the low side of the efficiency peak is much steeper than that on the high side.
So my suspicion was mostly correct. A PSU that has more than twice the capacity that it will be called on to supply will waste significantly more power than one being used in the 50% to 100% range.
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